Ever bought a second hand car?
Did that not come with second or even third hand tyres and brakes?
That's not to say anyone's personal opinion is right or wrong, just putting a bit of perspective on it as its not as simple as staying I'd never fit second hand, often you all ready have by buying a used car
Of course I have yes, who hasn't but part of the buying of a second hand car is looking at it and making a judgement on how the car has been treated, it's easy to see if a car has been cared for or if it's been mistreated, something you'd have no idea of if you bought second hand tyres, you have no idea where or what they came off and how they were treated.
For instance when I bought my R the wheels were in pretty much perfect condition (as was the rest of the car) which gave me confidence enough to think the tyres and brakes would also be in good condition, if the car had been jumped up kerbs or submitted to potholes the evidence would have been easy enough to see (especially with the profile of the 19"s)
To be honest though that is kind of beside the point because unless you have very deep pockets or factor it in to buying a new car then I don't know many people who budget for a set of new brakes and tyres after they buy a car (normally that would be negotiated if they are in or close to being in an unfit state) the point I was trying to make was that I would never knowingly purchase replacement tyres when I have no idea what has happened to them previously, they could have been stood for 6 months outside in all weathers and crack within days of being on your car or worse blowout at speed.
I will always buy new and as said if I can't afford to buy them I'd have to make other arrangements until I could.